Electrical insulation thermal softening detection device

ABSTRACT

A device to measure the thermal softening point of electrical insulating coatings on electric conducting members is described. The device includes an electrically conducting body, a cutting edge electrically attached to the body, an electric source and current sensing means in series with the insulated conducting test member. A weight is attached to one end of the test member to transmit a force to the test member and downwardly against the cutting edge. The sensing means is suited to respond when the cutting edge severs the insulation at the softening temperature; the heat being provided by a regulatable heating means.

United States Patent 191 Smith ELECTRICAL INSULATION THERMAL SOFTENINGDETECTION DEVICE [75] lnventor: Hugh B. Smith, Midland, Mich.

[73] Assignee: The Dow Chemical Comuany,

Midland, Mich.

22 Filed: July-2, 1971 [211 Appl. No.: 159,430

[52] US. Cl 73/15 R, 73/81, 324/54 [51] Int. Cl. G0ln 25/00 [58] Fieldof Search 73/15, 15.6, 17, 73/81; 324/54 [56] I References Cited UNITEDSTATES PATENTS 3,150,523 9/1964 Papsis 324/54 3,289,460 12/1966 Anderson73/17 3,580,047

5/1971 Simpson 73/17 [451 July 3, 1973 9/1965 Thompson 73/81 6/1965Ehlersl 0 73/17 Primary Examiner l-lerbert Goldstein Attorney-Robert W.Selby et al.

[57] ABSTRACT A device to measure the thermal softening point ofelectrical insulating coatings on electric conducting I members isdescribed. The device includes an electrically conducting body, acutting edge electrically attached to the body, an electric source andcurrent sensing means in series with the insulated conducting testmember. A weight is attached to one end of the test member to transmit aforce to the test member and downwardly against the cutting edge. Thesensing means is suited to respond when the cutting edge severs theinsulation at the softening temperature, the heat being provided by aregulatable heating means.

4 Claims, 2 Drawing Figures ELECTRICAL INSULATION THERMAL SOFTENINGDETECTION DEVICE BACKGROUND OF THE INVENTION Oftentimes it is desirableor necessary to employ inl sulated electrical wiring in environmentshaving a temperature in excess of ambient. It is highly desirable thatthe electrical conductor utilized for this purpose has an insulationcompatible with the temperatures of the environment. A means to rapidlyand easily determine the softening point of electrical insulation is'needed.

It is an object of this invention to provide a device to determine thetemperature at which electrical insulation softens. I I t It is anotherobject of this invention to' provide a device to rapidly and accuratelydetermine the thermal softening point of insulation on electricalconductors.

Other objects and advantages of this invention will become apparentduring the course of the following discussion.

SUMMARY OF THE INVENTION It has been found that the softeningtemperature of electrical insulation can be determined and thebeforementioned objects and advantages achieved in hereinafter describeddevice. The device for measuring the thermal softening point ofelectricalinsulating coatings on an elongated electrically conductingmember having a first and a second end comprises a body with a cuttingedge electrically attached to said body. The body is suitable to conductelectrical current from the cutting edge to an electrical sensing means.The cutting edge' is of a configuration suitable to sever the electricalinsulation at the thermal softening point of the insulation. A weight,characterized by being electrically insulated to prevent electriccurrent flow from the body to the conducting member, is adapted to beremovably, mechanically attached to the first end of the conductingmember. The weight causes a force to be simultaneously uniformly exertedin a downwardly direction on both the conducting member and the cuttingedge. An electric source is attached in electrical series with the body.The electric sensing means, adapted to respond to electric currentpassing through the conducting member, cutting edge and body from theelectric source, is removably electrically attached in series with thebody at the second end of the conducting member.

The device also includes a means to regulatably heat the insulatedconducting member to at least the softening temperature of theelectrical insulation. The heating means is suited to regulatablyincrease the temperature of the insulation, at least atthe cutting edge,to at least the softening temperature. When the softening temperature isattained, the cutting edge severs the insulating coating on theconducting member sufficiently to produce electrical contact between theconducting member and the cutting edge. Flow of electric current Ithrough the so-formed continuous circuit actuates the electric sensingmeans permitting the softening temperature to be accurately determined.

DESCRIPTION OF THE DRAWINGS The accompanying drawings further illustratethe invention;

FIG. 1 is a side view of the thermal softening detection device;

FIG. 2 is a side view of a preferred embodiment of r the thermalsoftening detection device.

Identical numerals, distinguished by a letter suffix 0 within theseveral figures represent parts having a similar function within thedifferent embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 4 In FIG. 1 is depicted a basicdevice for determining the softening temperature of electricalinsulation on an elongated electrically conducting member or wire 10having a first and a second end. The device comprises a body 12 suitableto conduct electric current and withstand the test temperatures withoutbeing deleteriously affected. The body 12 can be a solid or at leastpartially hollow block of a metal alloy, such as aluminum or copper, orother electrical conducting material, capable of withstanding theenvironmental testing conditions. A cutting edge 14 is integral with thebody 12; however, the cutting edge 14 need only be electricallyconnected to said body and be effectively heat stable at the testtemperatures. A weight 16 is preferably removably attached to the firstend of the wire 10. The means employed to attach the wire 10 to theweight 16 is not critical and can be tying, clamping, bolting and thelike. The weight 16 is of a suitable electric insulating material or isinsulated from the body 12 and/or the wire 10 to prevent sufficient flowof electricity from the body 12 through the weight 16 and the wire 10 toactuate an electric sensing means such as an ammeter, voltmeter, lightor bell 18. The bell 18 is removably attached to a second end of thewire 10 and to a jumper connector 20. Connector 20 is desirablyremovably attached in series to both the bell 18 and an electric sourcesuch as an AC or DC generator, commercially produced AC current, or a DCbattery 22. Theconnector 20 is of a material suitable to conductelectricity; such as copper oraluminum wire, cable, bus bar, and thelike. The specific position sequence of the bell l8, connector 20 andbattery 22 is'not critical as long as they are in electrical series withthe wire 10, body 12 and cutting edge 14.

A regulatable heating means such as an electrical heating element,flame, or a hot air blower 24is positioned in cooperative combinationwith the cutting edge 14. Such heating means are known to those skilledin the art and can be external and/or internal to the cutting edge 14and/or body 12.

In operation, the second end of the wire 10 is removably attached to thebell 18 by, for example, a standard electrical screw. The wire 10 issupportingly positioned over the cutting edge 14. The first end of thewire 10 is then preferably removably attached to the weight 16. The wire10, bell 18, jumper connector 20, battery 22, body 12 and cutting edge14 are in electrical series.

However, the insulation on the wire 10 prevents electrical contactbetween wire 10 and cutting edge 14 and, consequently, electric currentis prevented from passing through. the aforementioned electrical seriescircuit.

The hot air blower 24 is positioned adjacent to the cutting edge 14 andthe wire 10 so that heated air passes over and heats the wire at leastat the point at which it is supported by the cutting edge 14. Thetemperature of the air is gradually and regulatably increased until thesoftening temperature of the insulation coating on the wire 10 isattained. As the temperature approaches the insulation softening point,the weight 16, through the wire 10, exerts a downwardly directed forceon the wire 10 against the stationary cutting edge 14. As the insulationcoating on the wire 10 softens, the cutting edge 14 cuts or severs theinsulation coating sufficiently to produce electrical contact betweenthe wire 10 and the cutting edge 14. Upon electrical contact between thewire 10 and the cutting edge 14, electric current passes through theclosed loop series circuit from the battery 22 through the body 12,cutting edge 14 and wire 10 to cause the bell 18 to re spond to thecurrent and emit a sound. Upon actuation of the bell 18, the temperatureof the regulatably heated air and, therefore, the softening temperatureof the insulation on the wire 10 can be readily determined by methodsknown to those skilled in the art. Usually the weight employed isuniform from test to test to facilitate accurate comparison of thevarious softening temperature test results.

FIG. 2 is illustrative of another embodiment of the device comprising abody 12a, such as a bare or insulated electrically conductive wire.Preferably the body 12a is at least partially, permanently or removably,positioned within an electrically insulating body covering 23. The bodycovering 23 is of a material substantially stable at the testconditions, that is, the body covering 23 is not detrimentallyphysically or chemically altered by the test conditions. Examples ofsuitable body coverings are glass, thermosetting plastics such asphenolaldehyde, quartz and the like. A cutting edge 14a is of a materialsuitable to cut or sever at least part of the insulation on theconducting member or a-wire 10a. The cutting edge 1411 can be attachedelectrically to the body 12a or, as herein depicted, can be a part ofthe body 12a. For ease of positioning the wire 10a in physical contactwith the cutting edge 14a, at least one wire positioning means, such asa groove 26, is defined by the body covering 23 adjacent to the cuttingedge 14a. An electrical sensing means, such as an automatic recordingammeter 18a, is electrically attached by a jumper connector 20a inseries with an electric source, such as a generator 22a. The wire 10a,having a first end and a second end, is attached at the first end to aweight 16a. The weight 16a is of any material such as wood, ceramic,metal and the like. It is only necessary that electricity not fiow fromthe body 12a to the wire 10a through the weight 16a; this is readilyaccomplished by means known to those skilled in the art. Optionally asliding means, such as ball bearings 28, can be supportably positionedwithin the weight 16a and/or body covering 23 to minimize frictionbetween the weight 16a and the body covering 23 when the weight 16aexerts a downwardly directed force upon the wire A regulatable heatingmeans 24a is positioned at least adjacent to the junction of the wire10a and the cutting edge 14a. Preferably the cutting edge 14a isdisposed within the heating means 24a. The heating means 24a comprises aheat container ofa heat stable material, such as a ceramic or metal,supportably positioned in a spaced apart, at least partially incasingrelation with the junction. The heat container 30 is suited to transmitheat to the junction. A heating element, such as an electric unit 32, isexternally disposed adjacent to a wall portion of the container 30 tointroduce heat to the junction. To retard or prevent excessive heat lossfrom within the container 30 a thermally insulating coating 34 can,optionally, cover or enclose substantially all the exterior of theelectric unit 32 and the outer wall portions of the container 30. Suchinsulating coating 34 can be, for example, asbestos, ceramic foam or aheat reflecting shield as an aluminum sleeve. A

thermocouple 35 is position within the body covering 23 adjacent to thecutting edge 14a. A thermocouple 35 continuously measures thetemperature at about the point of physical contact between wire 10a andcutting edge 14a, hereinafter referred to as the junction. Anautomatically recording temperature instrument can optionally beelectrically attached to the thermocouple In operation, the first end ofthe wire 10a is physically connected to the weight 160, positionedwithin the groove 26, removably attached to a wire retainer 36, andremovably attached to the generator 22a. The heating means 24a is thensurroundingly placed over the wire 10a, cutting edge 14a and body 12a.The electric unit 32 is removably attached to a commercially availableelectric source external to the device and controllably heated toregulatably increase the temperature at the junction to the softeningtemperature of the insulation on wire 10a.

When the temperature at the junction attains the wire insulationsoftening point the cutting edge 14a severs the insulation andelectrically contacts the wire 10a, creating a continuous series circuitthrough the body 12a and the wire we to the recording ammeter 18a. Thetemperature at the junction when the ammeter indicates a current passingthrough the circuit can be readily determined from the thermocouple 35by well-known means. This temperature represents the softening point ofthe insulation coating on the wire 10a.

As is apparent from the foregoing specification, the device of thepresent invention is susceptible of being embodied with variousalterations and modifications, which may differ from those described inthe preceding description. For this reason, it is to be fully understoodthat all of the foregoing is intended to be illustrative and not to beconstrued or interpreted as being restrictive or otherwise limiting thepresent invention.

I claim: I

l. A device for measuring the thermal softening point of electricalinsulating coatings on an elongated electrically conducting member withtwo ends comprising:

an upwardly disposed, elongated body suitable to conduct electriccurrent;

a stationary cutting edge electrically attached to said body, saidcutting edge being of a configuration suitable to sever the insulationat the thermal softening point of the insulation;'

an electrically insulating body covering positioned adjacently aroundsaid body;

a conducting member positioning means defined by said body coveringadapted to position the conducting member in physical contact with saidcutting edge;

a thermocouple suitably positioned within the body covering to detectthe temperature at about said cutting edge;

a weight adapted to be removably mechanically attached to a first end ofthe conducting member to uniformly exert a downwardly directed force onthe conducting member and against said cutting sufficiently to causeelectrical contact between the conducting member and said body. 2. Thedevice of claim 1 wherein said body is a wire. 3. The device of claim 1wherein said heating means edge, said weight adapted to slidably move ona 5 includes a thermocouple positioned within said body surface of saidbody covering;

an electric source attached in electrical series with said body;

an electric sensing means removably electrically attached in series to asecond end of the conducting member and to said body to respond toelectric current passing through the conducting member and said bodyfrom said electric source;

a means to regulatably heat the conducting member to at least thesoftening temperature whereby the insulation softens at said cuttingedge and severs cover.

4. The device of claim 1 wherein said cutting edge is disposed withinsaid regulatable heating means, said heating means comprising a heatresistant and heat transmitting container, an electric heating elementex ternally disposed adjacent to a wall portion of said container, and athermally insulating coating surrounding substantially all the outerwall portions of said container and said heating element to retard heatflow from within said container and said cutting edge.

1. A device for measuring the thermal softening point of electricalinsulating coatings on an elongated electrically conducting member withtwo ends comprising: an upwardly disposed, elongated body suitable toconduct electric current; a stationary cutting edge electricallyattached to said body, said cutting edge being of a configurationsuitable to sever the insulation at the thermal softening point of theinsulation; an electrically insulating body covering positionedadjacently around said body; a conducting member positioning meansdefined by said body covering adapted to position the conducting memberin physical contact with said cutting edge; a thermocouple suitablypositioned within the body covering to detect the temperature at aboutsaid cutting edge; a weight adapted to be removably mechanicallyattached to a first end of the conducting member to uniformly exert adownwardly directed force on the conducting member and against saidcutting edge, said weight adapted to slidably move on a surface of saidbody covering; an electric source attached in electrical series withsaid body; an electric sensing means removably electrically attached inseries to a second end of the conducting member and to said body torespond to electric current passing through the conducting member andsaid body from said electric source; a means to regulatably heat theconducting member to at least the softening temperature whereby theinsulation softens at said cutting edge and severs sufficiently to causeelectrical contact between the conducting member and said body.
 2. Thedevice of claim 1 wherein said body is a wire.
 3. The device of claim 1wherein said heating means includes a thermocouple positioned withinsaid body cover.
 4. The device of claim 1 wherein said cutting edge isdisposed within said regulatable heating means, said heating meanscomprising a heat resistant and heat transmitting container, an electricheating element externally disposed adjacent to a wall portion of saidcontainer, and a thermally insulating coating surrounding substantiallyall the outer wall portions of said container and said heating elementto retard heat flow from within said container and said cutting edge.